This invention relates to the construction of concrete slabs, and in particular to a support structure that is rapidly and efficiently put in place, and rapidly and efficiently removed in condition for reuse.
Concrete slab construction is, of course, a routine method for horizontally covering open areas between columns and girders affixed to the walls of buildings, parking garages, and so on. A typical procedure for installing these concrete xe2x80x9cfloorsxe2x80x9d is to first place shoring members across the columns and girders, with shoring support posts rising from the ground or the deck below to the concrete floor being installed. Corrugated decking is then placed on the surface of the shoring, with the edges of the decking overlapping flange edges on the permanent building wall, girders and columns. Post-tensioning steel cables are then placed over the decking to add strength to the resultant structure. Conventional reinforcing bars can be used as well. Wet concrete is then poured over the corrugated decks. The concrete is then allowed to harden over a period of time. The supporting members can be so designed as to be removable after the concrete has hardened, simplifying concrete slab maintenance, and permitting re-use of the support structure on additional floors.
Various methods have been proposed for removable concrete slab support systems as is evident from the following examples. Keppler, in U.S. Pat. No. 1,707,226, discloses a supporting structure for concrete construction. This invention teaches a height adjustable shore 12 (centering post) cooperating with flanged 18 sheet metal members 16 (corrugated decking) connecting to height adjustable recesses 21 in soffit chairs. The invention notes (col. 2, lines 01-109), xe2x80x9cafter the concrete has been sufficiently set, the shoring may be removed and the ledgers taken down, whereby the centering forms with the soffit chairs may be removed and permanent shoring mounted in place to engage the soffit plates or boards for continuing to support the concrete until it is firmly set with full strengthxe2x80x9d. Lutz, in U.S. Pat. No. 3,059,738, discloses a removable concrete slab support wherein a portion of the support may be removed for the sake of economy prior to the concrete being fully set. An intermediate support 2 upheld by a prop 3 holds concrete slab supporting girders 1 and end supports 4 in place during the initial phase of setting wet concrete. Cornell, in U.S. Pat. No. 4,856,252, discloses a joist hanger 10 for removably securing a joist 38 during concrete slab construction. The joist hanger 10 has a box like metal configuration for securing the end of a suitable joist in the hanger. The joist hanger 10 has an extension section 18 for overlapping the top surface of a wall or girder 52, with a roll bar 22 acting as a pivot located a spaced distance below the extension section. After a concrete slab 34 is solidified on as suitable support 36, a sharp blow to the hanger causes it to pivot on roll bar 22, thereby releasing the hanger 10, joist, and support form the hardened concrete slab.
While these devices and methods disclose useful details for installation and removal of concrete slab support systems, they do not envision the efficiencies and conveniences inherent in the present invention. As will be more fully discussed below, this invention discloses a removable structure and method for supporting wet concrete during concrete slab construction without making use of vertical posts or shoring members which have to be supported down through the floors below to the ground. Accurate set up of corrugated decks is quickly accomplished to accept wet concrete. After the concrete has hardened all support members are quickly removed, ready for re-use as required.
It is therefore a primary object of the invention to provide a removable structure for supporting concrete slab construction that can be quickly put in place prior to the pouring of wet concrete, and quickly removed in re-usable condition after the concrete has hardened.
A further object of the invention is to eliminate the necessity for using vertical posts or shoring members which would have to be supported down through the floors below to the ground.
Another object of the invention is to permit the pouring and forming of a number of levels of concrete slabs in any desirable sequence.
Still another object of the invention is to provide for the plane of the shoring to always be automatically in the plane of the floor being formed.
A further object of the invention is to eliminate the necessity for permanently affixing structural support members to each other.
An additional object of the invention is to provide for most efficient placement of steel tendons within the concrete if post tensioning reinforcement concrete slab production is employed.
In my application Ser. No. 09/041,944, filed Mar. 13, 1998, which is now U.S. Patent No. 5,906,076, the disclosure of which is hereby incorporated by reference, I describe a removable support for concrete slab construction and method which achieves the above mentioned objectives and others. The above mentioned U.S. Patent disclosed vertically and laterally adjustable latches affixed to ends of shoring girders and shoring beans for quick connection to pre-cut holes in permanent building girders and columns, and shoring girders and shoring beams. Bearing shoes on a first end of corrugated decks cooperate with locking straps at a second end of said decks to complete the structural elements of the invention.
I have now discovered that the removable support for concrete slab construction in my application Ser. No. 09/041,944, filed Mar. 13, 1998, now U.S. Pat. No. 5,906,076, can be improved by replacing the disclosed vertically and laterally adjustable latches affixed to appropriate ends of shoring girders and shoring beams with latches which can be extended horizontally forward away from or retracted towards the ends of said shoring girders and shoring beams as will be more fully described below.
In building construction, concrete floors are routinely installed horizontally between permanent building columns and girders supporting the walls of the building. Wet concrete is poured over usually temporary corrugated decking erected between the building girders and columns. Typically shoring posts are required, the posts extending vertically from the ground or previously formed floor, in order to support the temporary shoring. For a variety of reasons, including economy in building construction and ease of maintenance of the finished building, removal of the corrugated decking, temporary shoring, and vertical post supports is desirable.
I have found that concrete floors can be constructed faster and more efficiently by eliminating any necessity for temporary vertical shoring supports. This permits forming floors at any convenient level without concerns regarding foundation supports for temporary shoring. In addition, my method provides for precise, accurate placement of temporary supports in that when all elements are positioned they are all in their proper location with minimal field measuring or adjusting.
For example, my method makes use of a right angle grid of shoring girders and shoring beams positioned between the permanent steelwork comprising the building columns and girders. The shoring girders and shoring beams can be constructed from conventional steel xe2x80x9cIxe2x80x9d beams with their ends modified with a latch device which allows insertion into a support for quick erection, adjustment, and removal. The purpose of the shoring girders is to provide support for the shoring beams, with the shoring beams providing the support for the corrugated decks. Conventional corrugated decking is employed with the exception that the ends of the decking to be supported by the building xe2x80x9cIxe2x80x9d beams have a bearing shoe added to the closed end of the corrugated decking to facilitate removal from the hardened concrete with will be more fully described below. The bearing shoe also prevents vertical displacement of the decking due to wind and other construction forces. The bearing shoe further allows exact bearing length of the decking over the building girder. Locking straps, placed at the opposite end of the decking to be supported by the shoring beams, complete the precise, accurately secured concrete slab construction support system.
To construct a concrete floor, the end latches on the shoring girders are secured in pre-cut holes in the permanent building girders and/or columns. Latches on at least one end of each shoring girder or shoring beam are affixed to the end of each support member by means of an adjustable shear plate. The shear plate can be moved a spaced distance forward or backward in relation to the length of the shoring girder or shoring beam, thereby permitting horizontal length adjustment between the latch and the building girder, column, or shoring beam. The latch affixed to the other end of the shoring girder or shoring beam can be similarly adjustable lengthwise, or the latch can be simply permanently secured by means of bolts or welds. Similarly shoring beams are quickly secured at right. angles to the shoring girders again making use of pre-cut holes in the shoring girders to which the end latches on the shoring beams are secured. Corrugated decking is then positioned perpendicular to and between the permanent girders and the shoring beams, with the bearing shoe end of the deck engaging a top flange edge of the permanent girder, and with the opposite end of the deck, overlapping the end of a second corrugated deck, and being held in position by locking straps, all supported by the shoring beams. The locking straps secure the open ends of the decking together, and also insure that the bearing shoe end of the deck is held firmly in place against movement caused by workers or the elements, as well as facilitating removal of the decking.
With the removable support structure now quickly, accurately, and firmly in place the wet concrete can be poured onto the surface of the corrugated decks with reinforcement rods inserted, if required. For those applications requiring post tensioning of the concrete, steel tendons can now be placed not only above the furrows of the decking, but also within the furrows. The more favored placement of steel tendons is possible here where the decking is secured perpendicular to the permanent girders, and not parallel thereto, which is typical in existing concrete slab construction. After the concrete has hardened sufficiently to be self supporting, the complete removable support structure is quickly removed, all components being ready for re-use. The latch mechanism on the shoring girders and shoring beams is removed after restraining bolts are removed, by simply hammering from the opposite side or by prying from the tab side. Latches are designed with a sloped end so that once the latch moves beyond the flat section of the connecting support member, the sloped surface helps to remove the latch and drop the shoring girder or shoring beam. The bearing shoe construction now permits the decks to be quickly removed from the cured concrete by simply lowering the open ends and rocking them in a downward direction, which movement can be facilitated by making use of the locking straps which had previously been holding the decks in place. The shape of the shoe end allows the rocking motion to break the deck free of the hardened concrete.
Thus a new convenience in forming concrete slabs in buildings, parking garages, and the like is disclosed. A wet concrete support structure is described which is set in place with heretofore unobtainable speed and efficiency. Vertical support posts for the shoring are completely eliminated, permitting flooring levels to be constructed in any convenient sequence, while at the same time assuring that the shoring is always automatically in the plane of the floor being formed whether level or on a slope as in ramped floors. The perpendicular placement of the corrugated decks also permits placement of post tensioning steel tendons in the most favored position for strengthening the concrete. While the shoring girders and shoring beams have been described as preferably being modified steel xe2x80x9cIxe2x80x9d beams, it is to be noted that other shoring materials, including wood, plastic, and concrete, can be similarly employed.